The present invention generally relates to bicycles, more particularly to a recumbent bicycle incorporating a conventional sit-up bicycle frame, the manufacture/assembly thereof, and, apparatus for cost-effectively forming a responsive, easy to ride recumbent bicycle using conventional sit-up bicycle components.
The frame is the most important part of a bicycle for many reasons. It providesxe2x80x94by the way it locates and spaces your saddle, crank set, and handlebarsxe2x80x94a geometry that positions a rider""s body for efficient pedaling. The same geometry also determines the handling, or behavior of a bike. How stablely it races down hill, its willingness to cut deeply into corners, and its ability to carry loadsxe2x80x94all of these factors are determined by the frame""s geometry. The bike""s general handling and comfort, and the rider""s position on it, are determined by its frame.
A conventional bicycle frame is often described by its two halves, the front and the rear triangles. The front triangle, also known as the main triangle, is actually a quadrilateral. It consists of the following tubes: the head tube, which is located at the front of the frame and holds the headset, or steering bearings; the top tube, which connects the head tube and the seat tube under your saddle; the seat tube, which runs from the seat down to the bottom bracket; and the down tube, which runs from the head tube down to the bottom bracket. The bottom bracket holds the bearings and axle of the crank set.
The rear triangle consists of the chainstays and the seatstays. The chainstays are the twin tubes that connect the bottom bracket and the two rear axle holders known as the dropouts. The seatstays are the twin tubes that connect the dropouts and the junction of the tubes under the saddle, called the seat cluster. Technically, the seat tube completes the triangle. However, when frame builders or bike mechanics talk about the rear triangle, they are usually referring only to the two sets of stays.
Completing the conventional frame are the fork and the steerer tube. The fork consists of two fork blades that are attached to a horizontal piece know as the fork crown. At the lower end of the blades are the two front axle holders known as fork tips or front dropouts. The steerer tube rises out of the crown at the top of the blades and is normally xe2x80x9chiddenxe2x80x9d (i.e., received) in the head tube. It connects the fork crown to the head set.
The traditional bicycle frame is generally known as the diamond frame, because of its shape, and historically referred to as the xe2x80x9cmensxe2x80x9d frame. Other conventional frame configurations include the xe2x80x9cladiesxe2x80x9d frame, wherein the top tube is replaced by a second down tube, which makes mounting and dismounting the bike easier, but eliminates much of its structural strength, and the mixte frame, which is a compromise between the diamond frame and the ladies frame, as the top tube is replaced with twin lateral tubes that run from the head tube all the way back to the rear axle. Of these three frame styles, the diamond frame still provides the best combination of rigidity, strength, and light weight.
Whereas most of today""s bicycles are of a conventional sit-up design, numerous attempts have been made to introduce recumbent bicycle designs. The recumbent bicycle is generally longer than a conventional sit-up bicycle, positioning a rider lower with respect to the ground, and is characterized by the rider sitting slightly reclined in a high-backed seat. The recumbent bicycle provides increased comfort, greater pedal efficiency, and a lower center of gravity when compared to the conventional sit-up bicycle. At present, single rider recumbent bicycles styles are generally characterized by their wheel base length: long wheel base (65-71xe2x80x3); short wheel base (33-45xe2x80x3); and, compact long wheel base (46-64xe2x80x3), with each style offering specific handling characteristics consistent with its frame configuration.
Despite their potential advantages in comfort (e.g., the generally reclined position of a rider, the notion of sitting in a xe2x80x9cchairxe2x80x9d, with a back support, as opposed to upon a xe2x80x9csaddlexe2x80x9d, ergonomic positioning of the handlebars either at shoulder level for xe2x80x9cabove seat steeringxe2x80x9d, or below the seat, xe2x80x9cbelow seat steering,xe2x80x9d at a position where a riders arms naturally hang), and their ergonomically superior power utilization potential (i.e., a pedal to seat relationship for an improved degree of pushing power), recumbent bicycles have met with limited commercial success.
Particularly burdensome has been the difficulty of working around the geometric limitations of the recumbent bicycle frame, that is to say, to design a bicycle that is practical, stable, safe, maneuverable, and above all else, easy to ride. A further, and equally important limitation to the general acceptance of recumbent bicycles has been their cost, a significant barrier to ownership. Because of their low production volumes, a recumbent bicycle tends to be significantly more expensive than a mass-produced upright bicycle.
Mayo, U.S. Pat. No. 5,951,034, discloses a kit for converting a regular upright bicycle into a semi-recumbent bicycle. An extension appliance, having a head tube and crank case, is provided for mating with the head tube of the frame of a conventional sit-up bicycle, so as to forwardly extend a front wheel relative to the rider""s position on and over the sit-up frame. In-as-much as Mayo provides an alternative, albeit cost effective, to specially produced or limited production recumbent cycles, the resulting frame geometry is less than desirable and awkward: more particularly, as the extension appliance is not a structural member, a recumbent frame so formed is greatly limited with respect to fundamental performance and handling.
A further problem with most bicycles is the degree of isolation from road shock the rider is afforded. This is particularly so with recumbent bicycles.
At a minimum, up-right bicycles (i.e., those having sit-up frames) allow the rider to stand on the pedals and raise off the saddle, thereby permitting his or her legs to effectively isolate the central mass of the rider from the impact and motion associated with travel over and through rough terrain, whether in an urban or rural setting. Standing on the pedals is not possible with semi or fully recumbent bicycles.
With the popularity of mountain and other xe2x80x9chybridxe2x80x9d all terrain bicycles, a great deal of progress has been made in the area of shock absorbing suspensions for the conventional, and not-so-conventional sit-up frame. However, such adaptations are only now appearing in the marketplace.
Therefore, a need exists in the art for an affordable recumbent bicycle having a frame which possesses the rigidity, strength and light weight associated with a diamond frame. Further, there exists a need in the art for such a recumbent bicycle wherein a suspension assembly for xe2x80x9csmoothing outxe2x80x9d the bumps is provided.
A recumbent bicycle, the manufacture thereof, and apparatus for forming same, is provided. The recumbent bicycle generally includes a frame having joined forward and rearward frame portions. The forward frame portion is a sit-up bicycle frame adpated to support a steerable front ground engaging wheel. The rearward frame portion is adapted to support a suspension assembly, and substantially bear a rider thereon.
Preferably, the sit-up bicycle frame includes a head tube, down tube, bottom bracket, seat tube, chainstay, seatstay, and dropouts. The rearward frame portion includes a supplemental chainstay and is generally joined to the forward frame portion such that the supplemental chainstay rearwardly extends from the dropouts as a substantial continuation or extension of the chainstay of the forward frame portion.
The apparatus of the subject invention permits transformation of a sit-up bicycle into a recumbent bicycle with a minimum number of additional parts required. The apparatus generally includes a frame extension appliance for affixation to the frame of the sit-up bicycle so as to rearwardly extend therefrom. The extension appliance is adapted to support a suspension assembly, and substantially bear a rider thereon. More specific features and advantages obtained in view of those features will become apparent with reference to the drawing figures and DETAILED DESCRIPTION OF THE INVENTION.